<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>

<body>
    <div id="app">

        <div class="imput-num">
            <button @click="sub"> - </button>
            <span>{{num}}</span>
            <button @click="add"> + </button>
        </div>
    </div>
</body>
<script src="../vue.js"></script>
<script>
    var app = new Vue({
        el: "#app",
        data: {
            num: 1
        },
        methods: {
            add: function () {
                console.log("加法成功");
                if (this.num < 10) {
                    this.num++;
                } else {
                    alert('加到头了')
                }
            },
            sub: function () {
                console.log("减法成功");
                if (this.num > 0) {
                    this.num--;
                } else {
                    alert("不得小于0");
                }
            }


        }
    })
</script>

</html>